1. Field of the Invention
The present invention relates to a method and apparatus for practicing the method of molding a continuous string or chain of interconnected elements or articles connected through molded scrap connectors. More particularly, the present invention relates to an integrated and continuous method, and apparatus therefor, of molding and winding a string of molded items into a tight coil.
2. Description of the Prior Art
Automatic assembly techniques for assembling a plurality of different components into a single composite product are well known. These techniques are employed, for example, in the assembly of anti-theft devices, such as those clamped to a garment in a store and which are capable of setting-off an alarm when passed through a suitable sensor, e.g., located at the door of the store.
In the molding of small parts in large quantities for automatic assembly, it is conventional to mold a predetermined number of parts in a single operation of the mold, after which the group of parts may be handled as a unit by virtue of their being connected together through scrap runners. The handling of such units during automatic assembly is, however, generally very inefficient in that it requires at least one person untangling and/or orienting the units and then feeding the individual units to the automatic assembly system. Any means of facilitating the automatic assembly of different parts, e.g., by making the feeding of parts to the assembly system more automatic and trouble free of entanglement and the need for correctly orienting the units, would be of great value to the industry.
In the molding of small parts, the molding of a continuous string of parts in spaced relationship and connected via scrap runners is known.
For example, U.S. Pat. No. 3,192,298 discloses a process for producing a runner of indefinite length with an indefinite number of molded articles secured thereto. In each successive molding operation of the process, the runner and its connected articles are removed from the mold cavity and are advanced so that only a small portion of the runner remains in the mold cavity to be connected to the runner of the next molding. Thereby, a runner of indefinite length is formed.
U.S. Pat. No. 2,569,083 discloses a method for molding a runner simultaneously with a plurality of articles to form a piece comprising the articles in spaced relation with respect to each other but connected through the medium of the runner. Upon removing the molded piece from the mold cavity, the trailing end of the runner is left in the mold cavity so that the leading end of the runner of tne newly molded piece is molded around the trailing end of the preceding piece. Thus, a chain of spaced, molded articles is formed.
In both of the afore-discussed processes, however, a great deal of resin is generally employed in the molding of the runner which is of a substantial structure. The runner is no more than a scrap runner, and thus a great deal of resin is wasted in a sense for non-article molding. As well, when the articles are removed from the runner, a great deal of scrap material has to be dealt with. The continuous string of articles provided by the afore-discussed processes are also in a form which would not facilitate easy shipment to an assembler followed by an automatic assembly of parts.
U.S. Pat. No. 3,655,308 also discloses a process for molding a continuous string of items, but with the items being successive sections of a plastic sheet. The sections are joined together at their edges during the molding process, so that the end product is a continuous plastic sheet.
U.S. Pat. No. 4,008,302 discloses a process for the molding of a succession of identical plastic parts in the form of a continuous web in which the parts are spaced from one another and secured to at least one continuous runner. The runner employed in the process can be any tape-like or other scrap portion employed during molding which is not a component of the molded part or parts, and which is provided to the mold from a continuous extraneous source. By employing a flexible web runner, a continuous chain of molded articles or parts formed by the process may then be wound and stored.
The problem with winding a continuous string of molded articles, however, is that the articles often cause problems during the unwinding due to the coil sagging and the string possibly becoming entangled. Thus, while shipment of the wound spool of articles to the assembler is facilitated, the package in itself does not facilitate the automatic assembly of the parts since the wound package must constantly be monitored due to the problems encountered in unwinding from the sagging of the coil of parts and/or entanglement of the parts. The problems encountered often result in stoppages and delays of the assembly line, and can also get so bad as to require that each part be cut from the coil and again be oriented and fed by hand to the assembly machine.
Thus, there is a definite need in the industry for an efficient and effective integrated process for preparing molded parts to be later assembled via automatic assembly in a form which not only facilitates its handling by the supplier, but which also truly facilitates the automatic assembly of the parts once received by the assembler. While of course a package which would facilitate automatic assembly could be made with much effort and time on the part of the supplier, for the process to be economically practical and commercially viable, it should also offer advantages to the supplier of the molded elements in the sense of an effective and efficient operation.
Accordingly, it is an object of the present invention to provide a most effective and efficient process for preparing a continuous string of molded parts in a form which facilitates its shipment to an assembler as well as the automatic assembly of the parts into a single composite product.
More particularly, it is an object of the present invention to provide an improved and integrated process and apparatus for preparing a wound coil of items which coil in itself facilitates the automatic assembly of parts by the assembler.
It is another object of the present invention to provide a continuous process which requires little supervision during the preparation of such a wound coil of items as well as the apparatus therefor.
It is another object of the present invention to provide a process and apparatus for molding a continuous string or chain of molded items without necessarily using a substantial amount of resin for scrap runners or connectors.
It is still another object of the present invention to provide a process and apparatus for molding a continuous string of discreet items whereby the advance of the string and withdrawal of the molded items from the mold are achieved without grabbing and distorting the parts.
Another object of the invention is to enable a continuous string of items to be wound-up without being excessively tensioned.